#include using namespace std; using lint = long long; using pint = pair; using plint = pair; struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_; #define ALL(x) (x).begin(), (x).end() #define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i=i##_begin_;i--) #define REP(i, n) FOR(i,0,n) #define IREP(i, n) IFOR(i,0,n) template void ndarray(vector &vec, int len) { vec.resize(len); } template void ndarray(vector &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); } template void ndfill(V &x, const T &val) { x = val; } template void ndfill(vector &vec, const T &val) { for (auto &v : vec) ndfill(v, val); } template bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; } template bool chmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; } template pair operator+(const pair &l, const pair &r) { return make_pair(l.first + r.first, l.second + r.second); } template pair operator-(const pair &l, const pair &r) { return make_pair(l.first - r.first, l.second - r.second); } template vector srtunq(vector vec) { sort(vec.begin(), vec.end()), vec.erase(unique(vec.begin(), vec.end()), vec.end()); return vec; } template istream &operator>>(istream &is, vector &vec) { for (auto &v : vec) is >> v; return is; } template ostream &operator<<(ostream &os, const vector &vec) { os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; } template ostream &operator<<(ostream &os, const deque &vec) { os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; } template ostream &operator<<(ostream &os, const set &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; } template ostream &operator<<(ostream &os, const unordered_set &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; } template ostream &operator<<(ostream &os, const multiset &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; } template ostream &operator<<(ostream &os, const unordered_multiset &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; } template ostream &operator<<(ostream &os, const pair &pa) { os << "(" << pa.first << "," << pa.second << ")"; return os; } template ostream &operator<<(ostream &os, const map &mp) { os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; } template ostream &operator<<(ostream &os, const unordered_map &mp) { os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; } #define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl; template struct ModInt { using lint = long long; static int get_mod() { return mod; } static int get_primitive_root() { static int primitive_root = 0; if (!primitive_root) { primitive_root = [&](){ std::set fac; int v = mod - 1; for (lint i = 2; i * i <= v; i++) while (v % i == 0) fac.insert(i), v /= i; if (v > 1) fac.insert(v); for (int g = 1; g < mod; g++) { bool ok = true; for (auto i : fac) if (ModInt(g).power((mod - 1) / i) == 1) { ok = false; break; } if (ok) return g; } return -1; }(); } return primitive_root; } int val; constexpr ModInt() : val(0) {} constexpr ModInt &_setval(lint v) { val = (v >= mod ? v - mod : v); return *this; } constexpr ModInt(lint v) { _setval(v % mod + mod); } explicit operator bool() const { return val != 0; } constexpr ModInt operator+(const ModInt &x) const { return ModInt()._setval((lint)val + x.val); } constexpr ModInt operator-(const ModInt &x) const { return ModInt()._setval((lint)val - x.val + mod); } constexpr ModInt operator*(const ModInt &x) const { return ModInt()._setval((lint)val * x.val % mod); } constexpr ModInt operator/(const ModInt &x) const { return ModInt()._setval((lint)val * x.inv() % mod); } constexpr ModInt operator-() const { return ModInt()._setval(mod - val); } constexpr ModInt &operator+=(const ModInt &x) { return *this = *this + x; } constexpr ModInt &operator-=(const ModInt &x) { return *this = *this - x; } constexpr ModInt &operator*=(const ModInt &x) { return *this = *this * x; } constexpr ModInt &operator/=(const ModInt &x) { return *this = *this / x; } friend constexpr ModInt operator+(lint a, const ModInt &x) { return ModInt()._setval(a % mod + x.val); } friend constexpr ModInt operator-(lint a, const ModInt &x) { return ModInt()._setval(a % mod - x.val + mod); } friend constexpr ModInt operator*(lint a, const ModInt &x) { return ModInt()._setval(a % mod * x.val % mod); } friend constexpr ModInt operator/(lint a, const ModInt &x) { return ModInt()._setval(a % mod * x.inv() % mod); } constexpr bool operator==(const ModInt &x) const { return val == x.val; } constexpr bool operator!=(const ModInt &x) const { return val != x.val; } bool operator<(const ModInt &x) const { return val < x.val; } // To use std::map friend std::istream &operator>>(std::istream &is, ModInt &x) { lint t; is >> t; x = ModInt(t); return is; } friend std::ostream &operator<<(std::ostream &os, const ModInt &x) { os << x.val; return os; } constexpr lint power(lint n) const { lint ans = 1, tmp = this->val; while (n) { if (n & 1) ans = ans * tmp % mod; tmp = tmp * tmp % mod; n /= 2; } return ans; } constexpr lint inv() const { return this->power(mod - 2); } constexpr ModInt operator^(lint n) const { return ModInt(this->power(n)); } constexpr ModInt &operator^=(lint n) { return *this = *this ^ n; } inline ModInt fac() const { static std::vector facs; int l0 = facs.size(); if (l0 > this->val) return facs[this->val]; facs.resize(this->val + 1); for (int i = l0; i <= this->val; i++) facs[i] = (i == 0 ? ModInt(1) : facs[i - 1] * ModInt(i)); return facs[this->val]; } ModInt doublefac() const { lint k = (this->val + 1) / 2; if (this->val & 1) return ModInt(k * 2).fac() / ModInt(2).power(k) / ModInt(k).fac(); else return ModInt(k).fac() * ModInt(2).power(k); } ModInt nCr(const ModInt &r) const { if (this->val < r.val) return ModInt(0); return this->fac() / ((*this - r).fac() * r.fac()); } ModInt sqrt() const { if (val == 0) return 0; if (mod == 2) return val; if (power((mod - 1) / 2) != 1) return 0; ModInt b = 1; while (b.power((mod - 1) / 2) == 1) b += 1; int e = 0, m = mod - 1; while (m % 2 == 0) m >>= 1, e++; ModInt x = power((m - 1) / 2), y = (*this) * x * x; x *= (*this); ModInt z = b.power(m); while (y != 1) { int j = 0; ModInt t = y; while (t != 1) j++, t *= t; z = z.power(1LL << (e - j - 1)); x *= z, z *= z, y *= z; e = j; } return ModInt(std::min(x.val, mod - x.val)); } }; constexpr lint MOD = 998244353; using mint = ModInt; vector> dp; // UnionFind, able to rewind to the previous state by undo() // Written for Educational Codeforces 62 F, although not verified yet. struct UndoSizeAwareUnionFind { using pint = std::pair; std::vector par, cou; std::stack> history; UndoSizeAwareUnionFind(int N) : par(N), cou(N, 1) { std::iota(par.begin(), par.end(), 0); } int find(int x) { return (par[x] == x) ? x :find(par[x]); } void unite(int x, int y) { x = find(x), y = find(y); if (cou[x] < cou[y]) std::swap(x, y); history.emplace(y, pint(par[y], cou[x])); if (x != y) par[y] = x, cou[x] += cou[y]; } void undo() { cou[par[history.top().first]] = history.top().second.second; par[history.top().first] = history.top().second.first; history.pop(); } void reset() { while (!history.empty()) undo(); } int count(int x) { return cou[find(x)]; } bool same(int x, int y) { return find(x) == find(y); } }; int main() { int N, M; cin >> N >> M; vector p(M); REP(i, M) { cin >> p[i].first >> p[i].second; } mint ret = 0; FOR(i, 3, N + 1) { ret += mint(N).fac() / mint(N - i).fac() / i; } dbg(ret); ndarray(dp, M + 1, 2 * M + 1); ndfill(dp, 2); FOR(e, 1, M + 1) FOR(v, 1, M * 2 + 1) if (N - v >= 0) { mint tmp = 0; REP(nins, N - v + 1) { if (v + nins < 3) continue; tmp += mint(N - v).nCr(nins) * mint(nins).fac() * mint(nins + e - 1).nCr(e - 1); } dp[e][v] = tmp * mint(e - 1).fac() * mint(2).power(e); } UndoSizeAwareUnionFind uf(N + 1); REP(S, 1 << M) if (S) { unordered_map cnt; uf.reset(); int pc = __builtin_popcount(S); int r = -1; REP(i, M) if ((S >> i) & 1) { cnt[p[i].first]++; cnt[p[i].second]++; r = p[i].first; uf.unite(p[i].first, p[i].second); } bool ok = true; int nb1 = 0; set vd1; for (auto pa : cnt) { if (pa.second > 2) ok = false; nb1 += (pa.second == 1); if (pa.second == 1) vd1.insert(pa.first); } int nok = 0, nbad = 0; for (auto pa : cnt) { int v = pa.first; bool flg = false; for (auto x : vd1) if (uf.same(v, x)) flg = true; if (flg) nok++; else nbad++; } if (nok and nbad) ok = false; if (!nok and uf.count(r) != pc) ok = false; if (!ok) continue; int e = nb1 / 2; int v = e + pc; ret += dp.at(e).at(v) * (pc % 2 ? -1 : 1); } cout << ret / 2 << '\n'; }